A press brake typically includes an upper piston or punch that is driven into sheet metal, deforming the sheet metal as controlled by a lower die. The upper punch may have an elongate V-shaped edge that causes the sheet metal bend along the edge of the tool, and the die defines a corresponding elongated V-shaped groove to control the bending of the sheet metal. Other shapes are used on the punch in cooperation with a die having a specific shape and size of elongate slot to produce various forms of bent sheet metal. The sheet metal to be bent in a press brake is placed between the punch tool and the die, and the punch tool, which is vertically aligned with the die, presses downwardly upon the sheet metal with sufficient force to bend the sheet metal into the shape defined by the die and the punch tool.
FIG. 1A illustrates a prior art or conventional press brake. The upper tool is a simple punch 12, although it should be understood that punches are often removably mounted to an arm so that different sized or shaped punches can be employed. A bottom tool 14 includes a base 20, a die holder 18, and a V-shaped die 16. A work piece 22 (i.e., a piece of sheet metal) to be formed is placed between punch 12 and die 16. In FIG. 1B, punch 12 has been forced to move downwardly, to contact work piece 22. As work piece 22 is forced into the V-shaped groove of die 16 by the punch, the work piece deforms. FIG. 1C shows punch 12 in a fully extended position, after work piece 22 has been formed into a configuration in which it is bent into about a 90° angle.
The specific configuration into which the work piece is formed by the punch and die is a function of the size and shape of the groove or channel defined by the die (and in some cases, a function of the punch size and shape). If a different configuration is required, then die 16 must be removed from die holder 18, and replaced with a die having a groove or channel appropriate to achieve the desired different configuration. While a plurality of different dies may provide the required flexibility to achieve a variety of required shapes when bending sheet metal, such flexibility comes at a cost. Press brakes are most often found in smaller commercial facilities where cost and efficiency are important concerns. The time required to remove a die and replace it with a different die reduces productivity. Further, the dies are relatively costly. While simple in shape, the dies can be quite massive, particularly for large press brakes. Also, to increase the service life of such dies, they are often formed of a hardened or tempered metal alloy, further increasing their cost. It would thus be desirable to provide a less costly press brake bottom tool die that is reconfigurable without replacing the die. It would further be desirable to provide a single press brake bottom tool die that can be used to produce a variety of different configurations when bending sheet metal, both to avoid requiring different dies, and to reduce productivity loss due to the time required to change dies.
A different type of prior art press brake die, which is manufactured by TSH International, of Tokyo, Japan, is shown in FIGS. 2A-2E. Instead of the working surface of the die comprising a single component having a fixed groove or channel, two movable dies generally shaped like half cylinders are disposed in corresponding elongate channels. FIGS. 2A and 2B respectively provide an end view and an isometric view of a wing die 30; the laterally extending plates on each die are not shown to simplify the drawing. Two elongate dies 32a and 32b, which are shaped like half cylinders, are disposed in corresponding channels 34a and 34b, at the top end of wing die 30. A plurality of springs 36 ensure that dies 32a and 32b return to their original positions after being moved during metal forming, as will be described in greater detail below. Channels 34a and 34b are formed into a base 38, and springs 36 are secured to base 38. Note that in addition to returning the dies to their original positions, the springs provide a desirable resisting force while bending metal.
As with other types of press brake tooling, wing dies are used in conjunction with an upper tool, shown as a punch 12a in FIGS. 2C-2E. Note that many different types of upper tools, or punches, are available. Both punch 12 of FIG. 1A-1C and punch 12a apply a top loading force against a work piece. FIGS. 2C-2E illustrate a somewhat modified wing die 30a that also includes dies shaped like a half cylinder, and which fit in corresponding channels in the base, similar to the elongate channels of wing die 30. However, dies 33a and 33b respectively include wings 35a and 35b, which extend beyond the half-cylinder shaped portion of the dies. A plurality of springs 36a are coupled to wing 35a, and a plurality of springs 36b are coupled to wing 35b. Thus, springs 36a are operative to return die 33a to its original position, and springs 36b are operative to return die 33b to its original position, after the force of the punch and the formed work piece are withdrawn. Again, the springs also provide a desirable resisting force when bending metal. Springs 36a and 36b are attached to each wing at spaced apart intervals along the longitudinal axis of the dies. Also, base 38a of FIGS. 2C-2E is smaller than base 38 in FIG. 2B. Wings are preferably included on dies of FIGS. 2A and 2B as well, although these wings are significantly smaller, providing only sufficient material to engage springs 36, and not forming a portion of the surface that assists in forming the work piece as the punch is advanced.
As shown in FIG. 2C, work piece 22 is placed on top of dies 33a and 33b, such that the area where the bend is to be formed is disposed at the juncture of dies 33a and 33b. Punch 12a is moved downward until it contacts the work piece. As work piece 22 is forced downwardly by punch 12a, dies 33a and 33b (on wing die 30a) tend to rotate about their respective longitudinal axes, within channels 34a and 34b, as can be seen by comparing FIG. 2C with FIG. 2D. Contrast FIG. 1B with FIG. 2D.
In FIG. 1B, the portion of work piece 22 immediately over the vertex of the V-shaped groove is unsupported. In FIG. 2D, more of work piece 22 is supported by the dies, reducing strain on the work piece. FIG. 2E shows punch 12a in a more fully extended position, illustrating that work piece 22 has been formed to have an approximate right angle bend. Springs 36a and 36b are under tension, ready to exert a restoring force upon dies 33a and 33b, respectively, to return the dies to their original positions, once punch 12a is withdrawn and the work piece has been removed.
While representing a substantial improvement over the prior art tooling shown in FIG. 1A-1C, particularly with respect to providing enhanced support to work piece 22, wing die 30a employs dies 33a and 33b (wing die 30 similarly employs dies 32a and 32b) that move apart from each other as the punch applies force against the work piece. Thus, there is not a fixed relationship between the two dies, and their spacing depends upon the extension of the punch. Also, wing die 30 and 30a are fixed tools, in that unlike die 16 of FIGS. 1A-1C, dies 33a and 33b of wing die 30a (and dies 32a and 32b of wing die 30) are not designed to be replaced with dies allowing different shaped bends to be achieved. This drawback is somewhat offset by the fact that continued advancement of punch 12a, past the partially extended position required to achieve a right angle bend, enables smaller angle bends to be achieved, as the sheet metal is forced further into the gap between the dies.
Still another type of prior art press brake tool is illustrated in FIGS. 3A-3E, which schematically show a ROLLA-V™ roller die 40 like that sold by Falcon Machine Tools Limited, of Stourbridge, UK. Similar to the wing die described above, roller die 40 includes two dies 42a and 42b that are shaped like elongated half cylinders, each respectively disposed in correspondingly shaped elongate channels 44a and 44b. While dies 42a and 42b are disposed on the upper portion of a base 48, no springs are included to return the dies back to their original positions.
FIGS. 3C-3E schematically illustrate roller die 40 and punch 12a being used to deform a work piece 22. In FIG. 3C, work piece 22 has been positioned atop the upper surfaces of dies 42a and 42b, with the area where the bend is to be formed disposed at the juncture of dies 42a and 42b. In FIG. 3D, punch 12a has been forced downwardly to contact work piece 22, beginning the deformation or bending process. Again, as work piece 22 is forced downwardly into dies 42a and 42b, the dies rotate within their respective channels 44a and 44b, providing support for the work piece, but rotating apart as the punch advances. FIG. 3E shows punch 12a in a more fully extended position, after approximately a 90° bend has been formed in work piece 22. Again, this prior art device also suffers from the same drawback as the press brake shown in FIGS. 2A-2E; namely, the gap between the dies increases as they rotate, so that the spacing between the dies does not remain fixed, but instead changes as a function of the extension of the punch, increasing as the angle of the bend increases.
It would be desirable to provide a press brake bottom tool die that enables superior support for a work piece as compared to the prior art dies, such as those discussed above. It would further be desirable to provide a bottom tool in which the spacing between the dies remains fixed while the die is used. Preferably, this press brake die assembly should include adjustment features enabling a variety of bends to be formed with a single die assembly.
It is further desirable to provide a press brake bottom tool die that enables short leg bends to be achieved. Short leg bending refers to forming a bend in a piece of sheet metal relatively close to an edge of the sheet metal, such that a short leg is defined between the bend and the edge. Most existing tooling does not facilitate short leg bending.